1. Technical Field
The present invention relates to a molding method for an endless crawler which is mounted and used on a construction vehicle or a high-speed snowfield vehicle such as an RV or the like.
2. Background Art
In recent years, the number of cases has risen in which ordinary driving wheels on a leisure RV vehicle are removed and a crawler driver formed of a plurality of sprockets and rotation wheels is mounted in order for the vehicle to be used as a snowfield vehicle or the like. A crawler structured of an endless rubber belt and the like is mounted on the crawler driver. However, the need to accommodate a trend in higher traveling speed has been a prime concern attendant with mounting a crawler on an RV vehicle. Further, accommodating the crawler to a higher traveling speed has been a pressing concern not only with ordinary snowfield vehicles and the like but with construction vehicles on which rubber crawlers which reduce noise and vibration have come to be mounted.
Generally, a crawler mounted on the crawler driver is molded and vulcanized according to such methods as those illustrated in FIGS. 9A and 10C.
FIGS. 9A to 9C illustrate a basic production method. A crawler 70 illustrated in FIG. 9A, which is formed of a belt-shaped rubber and the like in which reinforcing cords (not illustrated) are embedded, is nipped by an upper mold 74 and a lower mold 72, as illustrated in FIG. 9B. The upper and lower molds are further nipped by an outer heating plate 76 and an inner heating plate 78 to vulcanize the crawler 70 by heating. Thereafter, as illustrated in FIG. 9C, staggered end portions 70A and 70B of the crawler 70 are overlapped with each other, and then both end portions are vulcanized and joined by a lower mold 80 and an upper mold 82 and by an outer heating plate 84 and an inner heating plate 86 to obtain an endless crawler product.
FIGS. 10A to 10C illustrate a production method known as feed vulcanization which is used when vulcanizing a comparatively lengthy crawler. A crawler 70 illustrated in FIG. 10A, which is formed of a lengthy belt-shaped rubber and the like in which reinforcing cords (not illustrated) are embedded, is nipped by a lower mold 80 and an upper mold 82, as illustrated in FIG. 10B. The lower mold 80 and the upper mold 82 are of a relatively short predetermined length, and are further nipped by an outer heating plate 84 and an inner heating plate 86 which vulcanize a predetermined length portion of the crawler 70 by heating. This is sequentially repeated so that the entire length of the crawler 70 is vulcanized. Thereafter, as illustrated in FIG. 10C, staggered end portions 70A and 70B of the crawler 70 are overlapped with each other, and then both end portions are vulcanized and joined by the lower mold 80 and the upper mold 82 and by the outer heating plate 84 and the inner heating plate 86 to obtain an endless crawler product.
However, the production process for crawlers molded in accordance with such conventional vulcanization methods requires an excessive amount of time because the molding of the crawlers is conducted in advance in separate processes before entering the vulcanization process.
The vulcanization method illustrated in FIG. 9 requires not only a setting site with a large amount of space because the mold and the heating plate become longer and larger, but also requires a joining-vulcanization process just for the ends.
The vulcanization method illustrated in FIGS. 10A to 10C requires that vulcanization be repeated from a few times to as many as ten times for each predetermined length even though the mold and the heating plate are compacted. In addition, this method requires an excessive amount of time for vulcanization and, similar to the vulcanization method illustrated in FIGS. 9A to 9C, a joining-vulcanization process just for the ends.
Moreover, in these production methods which use vulcanization, it is impossible to endow the endless ring-shaped crawler belt with uniform properties at every point on the circumference of the crawler, since both longitudinal end portions of the belt-shaped crawler must be vulcanized and joined. Further, the process of connecting respective, paired end portions of reinforcement cords which are plurally provided in a row in the lengthwise direction of the crawler and embedded therein is burdensome. With regard to reinforcement strength, there has also been the fear that the continuity might be severed, not to mention the impossibility of embedding spiral reinforcement cords that could make a circumferentially uniform reinforcement strength possible.
Conventional production methods which employ vulcanization have thus been unable to accommodate the rotation of the crawler at a high speed accompanying a higher vehicle speed.
Therefore, the present applicants proposed a crawler molding method (see JP-A No. 9-76369) and a crawler molding device and a molding method thereof (Japanese Patent Application No. 9-355208) so as to solve the problems described above in conventional molding and vulcanization methods. The crawler molding device and molding method thereof disclosed in Japanese Patent Application No. 9-355208 relate to an inner mold and release of the inner mold. In the seamless crawler molding method disclosed in JP-A No. 9-76369, the number of production steps is few, endowing the crawler with a circumferentially uniform strength property is made possible, and the embedding of spiral reinforcement cords in the rubber crawler and the like which can accommodate high-speed traveling is made possible.
An object of the present invention is to mold a seamless crawler which improves upon the proposed crawler molding device and molding method mentioned above, and in which the number of production steps is few, embedding of spiral reinforcement cords and a circumferentially uniform strength property are made possible, which can further accommodate high-speed traveling, which enables a uniform, reliable outer mold pressure, and in which a seamless crawler can be molded only by adding or removing a portion of the mold, even for crawlers whose circumferential lengths are different.
Means for Solving the Problems
The invention provides a crawler molding method, in which structural components of a crawler are placed between an outer mold and an inner mold to form an endless shape and vulcanized to integrally mold a crawler, comprising: disposing the structural components of the crawler on an outer peripheral surface of an inner mold, which inner mold is dividable in the axial direction of the crawler; and thereafter radially contracting and pressurizing toward the inner mold by a radially contracting means a diameter of a circle defined by a plurality of outer molds which are divided and disposed along the outer peripheral surface of the inner mold, whereby the structural components of the crawler are integrally vulcanized.
The invention provides a crawler molding space which is formed by an outer peripheral surface of the inner mold and an inner peripheral surface defined by the plurality of outer molds is circular from a side view.
The invention provides the inner mold is structured by two semi-circular inner molds and by a plurality of square inner molds which are disposed between the semi-circular inner molds and which allow the outer peripheral surfaces thereof to be continued; and the outer mold is structured by a plurality of circular arc-shaped outer molds to form a crawler molding space between the outer molds and the semi-circular inner molds, the crawler molding space being semi-circular from a side view, and by a plurality of square outer molds to form a linear crawler molding space between the outer molds and the square inner molds.
The invention provides a length of the square outer molds is determined by a crawler pitch such as an interval between driving sprocket holes of the crawler or the embedded metals, and a number of square outer molds to be used is determined by a circumferential length of the crawler.
The invention further provides the radially contracting means is formed by a radially contractible inner frame in which an inclined surface which is disposed on an inner peripheral surface side of the outer mold and which inclines in the width direction of the crawler is formed on an outer peripheral surface of the inner frame, and an outer frame in which an inclined surface which slides along the inclined surface formed on the outer peripheral surface of the inner frame is formed on an inner peripheral surface of the outer frame; and the structural components of the crawler are integrally vulcanized by moving the outer frame in the width direction of the crawler to radially contract and pressurize the inner frame and the outer molds.
The invention provides a press plate for pressing the outer frame in the width direction of the crawler.
The invention further provides the radially contracting means is structured by inclined surfaces formed on both end portions of the outer mold in the width direction and by an outer frame which is disposed on both sides of the outer mold and in which inclined surfaces which slide along the inclined surfaces formed on the both end portions of the outer mold is formed on an inner peripheral portion of the outer frame, and the outer frame is moved toward the outer mold from the both sides, so that the outer mold is radially contracted and pressurized to integrally vulcanize the structural components of the crawler.
The invention provides at the time that the inner molds are divided in the width direction of the crawler and the crawler is released, an outer peripheral portion of the crawler is gripped by a gripping means.
The invention further provides the gripping means is a gripping member which is driven by a gripping cylinder and which grips an outer peripheral portion of the crawler between the inner mold and the gripping member.
The invention provides the inner mold is rotated, and a reinforcement cord which is fed from a wire feeder to an outer peripheral surface of the inner mold is wound.
The invention further provides the inner mold is mounted on a mold chuck which is rotatably driven by a motor.
The invention further provides the inner mold is mounted on a mold release driver which moves relative to rails.
The invention further provides the mold release driver is driven by a cylinder.
The invention provides reinforcing wires are coiled as a single reinforcement cord in a spiral configuration to an embedding site on the crawler at a predetermined pitch while being twisted together from the wire feeder.
The invention further provides a reinforcement cord formed by the wires which have been twisted together in advance is fed from a wire feeder in a spiral configuration.
The invention further provides a reinforcement cord which has been coated with rubber is fed from a wire feeder in a spiral configuration.
The invention provides a canvas-configured body, in which a plurality of reinforcing cords is mounted in one of a row and at an incline at a predetermined bias angle, is fed from the wire feeder.
The invention provides the inner mold is divided in three at a center and both sides of the center.
The invention provides a tread pattern of a tracking surface of the crawler is defined by an inner peripheral surface of the outer molds.
The invention further provides the inner mold and the outer mold are heated as heating plates.
Effects of the Invention
As stated in detail above, in accordance with the present invention, the structural components of the crawler are molded at the outer periphery of the inner mold which is dividable in the axial direction. Thereafter, the outer mold which is divided in the circumferential direction and slidable in the radial direction is disposed at the outer side of the structural components of the crawler. The outer mold is radially contracted by a pressure applied thereto, whereby the structural components of the crawler are vulcanized. Therefore, when the structural components of the crawler are molded at the outer periphery of the inner mold, it becomes possible to embed a reinforcement cord in a spiral configuration by using a wire feeder. In addition, between an endless ring-shaped outer mold and inner mold, the structural components of a crawler can be pressurized uniformly and reliably at a circumference by a plurality of outer molds. Molding and vulcanization are simultaneously carried out, and mold release is rapid. Thus, it becomes possible to sharply reduce the amount of work time.
Further, the outer periphery of the outer mold is made into an inclined surface which inclines in the axial direction. An outer frame, on which an inclined surface which corresponds with the inclined surface at the outer periphery of the outer mold and which is provided at the inner periphery of the outer frame, is disposed at the outer side of the outer mold. The outer mold is radially contracted by pressure applied thereto from a movement of the outer frame in the axial direction. Therefore, when structured so that the structural components of a crawler are vulcanized in this way, linear movement of the outer frame in the axial direction which is relatively easy to control can be converted to the contraction of a plurality of outer molds in the radial direction, through the inclined surface, which outer molds are divided in the circumferential direction when the molding and vulcanization are carried out. Uniform and reliable pressure can thereby be applied to the endless ring-shaped crawler at the circumference. Thus, a crawler having uniform properties at every point on the circumference can be manufactured.
Further, when the outer mold is structured such that the mold portions which come into direct contact with the structural components of the crawler and inner frame portions at the outer periphery thereof are separate bodies, the inner frame can be selected to a material suitable for sliding with the outer frame along the inclined surface, and the outer mold can be selected to a material suitable for vulcanization. Thus, freedom of choice in the design stage in selecting materials can be increased.
A molding method for a seamless crawler is provided in which the number of production steps is few, embedding of spiral reinforcement cords and a circumferentially uniform strength property on the circumference of the crawler are made possible, high-speed traveling can be accommodated, and a uniform, reliable pressure for an outer mold is enabled. Unlike conventional crawler molding methods, there is no need to be troubled with joining processes for paired end portions of reinforcement cords which are plurally provided in a row and embedded. Continuity with respect to reinforcement strength is maintained. By securing a stable reinforcement strength, stability of the crawler at high-speed traveling can be improved and long life is ensured.
In addition, the number of square inner molds and outer molds can be selected in accordance with the circumferential length of the crawler to be formed, so that a variety of crawlers having different circumferential lengths can be integrally vulcanized and molded at a low cost by using in common the front and rear semicircular inner molds without changing thereof.